Tell me about alcohol free fragrances - how different are they to
'normal perfume / fragrances'. Why do they make them?
Any tips or hints about who should wear them, use them and who
manufactures / retails them. (UK based answers please)

Here's a partial answer that may steer your search in the right
direction:  A good amount of the students at my Univeristy (U.S.) do
not wear perfume unless it is alcohol free because they are Muslims. 
Others feel that the alcohol on your skin can cause irriatation and
drying.  Here is a link to back up this hearsay:

http://www.captaincompany.com/Perfumes4U/WhyAlcoholFree.asp

The english grammar isn't great on the site, but you get the point.  I
also wouldn't take the source as authoratative, as they are in the
perfume selling business.  I am not a Muslim so I cannot say from
personal knowledge why exactly one must use alcohol-free perfume.